LED devices are more and more popularly used as light sources for different applications, such as backlight modules for liquid crystal displays (LCDs) or a variety of kinds of lamps. Following the evolution of packaging technology of LED chips from chip on board (COB) packaging to flip chip packaging and chip scale package (CSP) packaging, illumination angle of the LED chip is increased from top illumination for COB packaging to top and side illumination for flip chip packaging and CSP packaging.
Generally an optical lens is located over an LED chip to adjust a light filed generated by the LED chip to a required one. A bottom part of the side illumination generated by the LED chip of flip chip packaging or CSP packaging passes through a lateral side of the optical lens and propagates completely laterally, which does not contribute any usefulness for the desired illumination. The desired illumination needs the light to propagate at least partly forwardly.